Cutting head for a dry shaver



May 16, 1967 FIG. 1

B. FUTTERER ETAL CUTTING HEAD FOR A DRY SHAVER original Filedl oct. 14, 1963 BODO FU TTER ER WER NER M ESS l NGER ATTO R N EYS United States Patent O s claims. (ci. sti-43.92)

The present application is a divisional application of copending application Ser. No. 316,095 filed Oct. 14, 1963, now abandoned, which is, in turn, derived in part from application Ser. No. 84,586 filed on lan. 24, 1961 and abandoned after the filing of said application Ser. No. 316,095.

This invention relates more particularly but not exclusively to dry Shavers of the type in which an inner cutting part or element such as a number of knives rigidly interconnected to form a knife block is reciprocated by a vibrating armature motor while being pressed against the inner face of a stationary foil cutting comb or perforated cutting foil which serves as the outer cutting part, the inner and outer cutting elements constituting Va cutting head. The invention is more especially concerned with a novel system of mounting the knife block on the driving component and with its coaction with the cutting foil.

In a known shaver of this type, the knife block is connected to the oscillating lever of the -drive motor through a universal coupling which allows some movement of the block about its three principal axes, longitudinal, transverse and vertical. This cutting head has the disadvantage of permitting the knife block to wobble somewhat about its longitudinal axis and thus it is not able to take up lateral thrust during shaving, and does not engage the cutting foil properly. This resul-ts in poor cutting eiliciency. The performance can be improved in this respect by using a pin at the transverse axis of the knife block to link the latter wit-h the oscillating lever. This arrangement is known as a semi-universal coupling since it allows movement about two out of the three principal axes of the cutting block.

In Shavers in which there is a single helical compression spring mounted on the driving pin of the oscillating lever for loading the inner cutting part, the effect on shaving or cutting efficiency of the engagement of this spring with the knife block has been largely overlooked. Thus, if the end of the spring rests directly against the underface of the knife block, asymmetrical and otherwise uneven loading of the spring in the extreme positions of the oscillating lever results in and leads to disengagement of the end knives from the cutting foil.

A third difficulty is the cleaning of dry Shavers. For this the knife block must, at regular intervals, be cornpletely freed of skin debris, sebum `and the like. It should be able to be removed without specially adapted tools or other additional equipment to allow a cleaning liquid such as benzine to be applied and washed off. Easy removal of the knife block also facilitates any necessary repairs.

One effect of the improvements of our invention is the provision of a dry shave cutting head of the type comprising a knife block to be reciprocated by an oscillating lever, itself carrying a spring for pressing the head against the inside of the cutting foil which is free from al-l the above faults and has a knife block which is connected to the driving element in such a manner that the knife block cannot rock about its longitudinal axis while rocking about its transverse axis nor cause additional loading of Mice the spring. The value of this coupling between the inner cutting part and the drive of a dry shaver is demonstrated by the absence of .parasitic vibration and the consequent quiet running of the knife block.

To achieve this and other advantages which will appear as the description proceeds, we arrange the spring to abut against a sliding bushing mounted on a pin attached to the oscilla-ting lever. The bushing is coupled to the knife block to pivot about the latters transverse axis in such a manner that the 4permitted rocking movements of the knife block about its vertical and transverse axes do not place additional strains on the spring. Preferably the knife block is detachably secured to a cross head by a known snap-fastener type of connection. The bushing and the cross head are both so arranged that the former, which is journalled in the latter, can pivot about the transverse axis of the knife block. The use of the sliding bushing also enables us to allow the cross head and the structurally -associated knife block to slide along, and to rock about the preferably cylindrical end of the oscillating lever. rDherefore, the spring presses the knife block evenly against the cutting foil and is itself not asymmetrically loaded. Running is quiet while disengagement of the knife block from the cutting foil at the outer edges is prevented.

We prefer to make the cross head in the form of a plate with a central opening in which the bushing is pivotally mounted. On the side of this plate facing the underside of the knife block, at each end of the central opening, we provide the tensioning means for the snap-fastener connection, e.g. hooked projections.

A cross head plate with marginal flanges or portions set at an angle to its main plane has been found especially successful since the hooked projections can be placed at the ends of these marginal portions while the bearings for the bushing can be placed in the middle of them. The end of the spring carried on the oscillating lever surrounds the outer face of the bushing and lies in the latters pivotal axis.

The knife block has an elongated, frame-like base plate carrying two pins aligned with, and engaging tensioning means (the hooked projections) on the cross head so as to cooperate with them to produce t'he snap-fastener connection.

We lind it especially convenient to place the hooked projections in two pairs which are arranged on each side of the central opening in the plate of the cross head so that they are symmetrically placed with respect to counter abutments. The advantage of this is that one pushing the pins of the knife block between the hooked projections and the 4abutments effects a three point engagement of each pin so that the connection between the knife block and the cross head does, in fact, possess a double snapfastener action. This effects a good distribution of the weight of the knife block and of the thrusts of the drive through the equivalent of two snap-fasteners so that attachment is secure, chatter is prevented and the cutting action improved.

In a preferred form of our novel shaver, the base plate of the knife block has upwardly projecting hemispherical end Walls which are linked by a bridge overlying the base plate. The knives or knife blades which extend normal to the base plate and its longitudinal axis are attached to the base plate and bridge by casting during production thereof so as to form one integral assembly. This form of knife block has the advantage of having a center of gravity which is sufficiently 10W to be coplanar with the coupling pins placed symmetrically about the center of the block. The transmission of thrusts from the oscillating lever to the knife block therefore takes place in the plane of the center of gravity and the thrust per unit area of all the knives against the cutting foil is equal. This improvement reduces chatter, which has already been discussed and therefore further improves cutting action.

In order to prevent the knife block from coming away when the cutter frame is detached, we find it expedient to tix a spring disc on the top end of the oscillating lever to limit travel of the cross head and bushing.

Since the knife block is hollow and open downwards, we find it expedient to close it on this side by making the cross head of sufficient length to serve this purpose and receive hair dust In order to collect this dust, we provide on the cross head a removable hair-collecting adhesive insert on which the hair debris gathers. This has the advantage that the whole interior space of the knife block is utilized as a hair-collecting container. On removing the knife block, the adhesive insert can be restored or replaced.

Though we have referred above almost exclusively to a cutting head with a knife block, the various novel features which we propose could also be applied to a shaver in which the inner cutting element is a cutting grid or perforated sheet.

Further details and advantages of our novel improvements in dry Shavers will now appear from the following particular description which refers to a novel shaver head shown in the attached drawing, and is to be considered purely illustrative.

The figures show:

FIG. 1 is a cross section of the cutting head of the dry shaver;

FIG. 2 is a longitudinal section omitting the parts securing the cutter head frame to the housing; and

FIG. 3 is a plan view of the cross head on a larger scale, the support pins of the knife block being shown in broken lines.

The knife block 1 or movable cutter of the cutting head which is mounted in the housing 1 and arranged to be driven by the oscillating lever 2, comprises a framelike base plate 3, which is open so as to give access from below. The knife block has semi-circular upwardly projecting end walls 4 (see FIG. l) which are connected to a bridge 5. The so-formed basic skeleton of the knife head or block is made by die casting using a known incasting technique so that their knives 6, normal to the longitudinal axis of the block, are each attached at three points, at the bridge 5 and at each of the longitudinal side pieces of the base plate 3. `When it is remembered that the shaver is mostly moved over the skin while held at a right angle to it, the advantage of this arrangement will be seen: the greatest thrust on the semi-cylindrical knife block through the thin, iiexible foil or stationary cutter 18 will occur along the median line of its semi-cylindrical face area and will be taken up by the bridge 5 placed in this very position and transmitted through the end walls 4 to the base plate. We have not shown the knives 6 in FIG. l in order to make one end wall 4 visible.

The knife block is linked through a cross head 7 of thermoplastic synthetic resin with the oscillating lever 2. The cross head 7 has the form of a rectangular plate with a central opening S (see FIG. 3) in which a bushing 9 is mounted by means of trunnions 10 journalled in the turned-up or angled longitudinal marginal portions or iianges 7'. The trunnions or pins 10 are arranged at the ends of a yoke 10 on the bushing 9.

The latter has a bore 48 enabling it to be slid along, and turned about a cylindrical pin 11 on the oscillating lever 2. The outer face of the bushing iits into and guides the end coils of a compression spring 12 mounted on the pin 11. The compression spirng 12 engages the yoke so that it cannot move upwards. The yoke defines the pivot axis of the bushing 9.

The knife block is attached to the cross head 7 by a connection resembling a double snap-fastener. For

this purpose, the longitudinal sides of the base plate 3 of the knife block carry axially split pins 13 at points which are symmetrically placed about its center and coplanar with its center of gravity (see FIG. 2). These pins 13, which are of tubular spring steel, are deformed before insertion in the knife block so that on recovering their shape after insertion positive connections result. The pins or tubes 13 rest against two pairs of hooked projections 14 and 1S and against aligned corresponding counter-abutments 16 and 17 on the cross head 7. The abutments and projections thus form a three point attachment for each pin (as shown in FIG. 3 in broken lines) so that a slight pull or push with the `iingers is sufficient to remove or replace the knife block. This greatly simplifies repairs and facilitates cleaning and disinfecting, more so since the knife block is best taken off to avoid getting cleaning liquid on or in the synthetic resin housing.

For each movement of the oscillating lever 2, the knife block makes a relative rocking movement about its transverse axis in the trunnions 10 and the yoke 10 of the bushing. It also makes a relative linear movement along the axis of the oscillating lever 2. This rotary and linear movement guarantees the best use being made of the compression spring 12 since it is not bent to one side in opeartion and undesired parasitic vibrations are excluded. The spring is only subjected to compression, not flexure, and its loading is minimal. The reciprocation of the knife block under the stationary cutting member or cutting foil comb 18 is completely independent of spring pressure so that disengagement of the end knives from the foil 18 in the extreme positions of travel of the knife block does not occur. Consequently, the cutting action in these marginal zones is very eiiicient.

In addition to these two movements, the knife block can also rock about its vertical axis to adapt itself to the hollow of the cutting foil 18. Moreover, when the cutting head frame 19 is removed, the knife block can be more easily removed from the cross head 7 after turning it from the working position. In order to avoid undesired removal of the knife head when only the cutting head is to be taken off, a spring locking washer 20 is fixed to the end of the pin 11 on the oscillating lever 2 to limit upward movement of the bushing.

Various modifications can be made in the novel shaver as described. Thus, the base plate of the cross head 7 could be made suiiiciently long to close the knife block frame completely from below. Hair dust and other debris would then be collected by the base plate. The face of the latter turned towards the knives could be covered with a removable adhesive insert (not shown) to which hair dust would stick and from which it could be removed in the course of cleaning.

We claim:

1. In a dry shaver, in combination: a housing; a cutting head mounted on said housing and including a movable cutter and a stationary cutting foil overlying said movable cutter; oscillating means in said housing and including an oscillating lever for reciprocating said movable cutter along the inner surface of said cutting foil; coupling means including a bushing slidably mounted on said lever for reciprocation in axial direction of the latter; a plate formed with a central opening therethrough through which said bushing extends and being pivotally connected to said bushing tiltable about a fixed axis transverse to the axis of said lever; and connecting means for releasably connecting said movable cutter to said plate; and spring means engaging at one end thereof against said lever and at the other end against said bushing of said coupling means and tending to move the latter and said movable cutter connected thereto in direction of the axis of said lever toward said cutting foil whereby said spring means is stressed only due to reciprocation of said bushing in axial direction of said lever and is not stressed due to relative tilting movement of lever and plate about said transversely extending axis.

2. VIn a dry shaver, in combination: a housing; a cutting head mounted in said housing and including a movable cutter and a stationary cutting foil overlying said movable cutter; an oscillating lever in said housing for reciprocating said movable cutter along the inner surface of said cutting foil; coupling means including a bushing slidably mounted on said lever for reciprocation in axial direction of the latter, a plate formed with a central opening therethrough through which said bushing extends and being pivotally connected to said bushing tiltable about a `fixed axis transverse to the axis of said lever, and resilient connecting means for releasably connecting said movable cutter to said plate and permitting removal of said movable cutter from said plate substantially in direction of the axis of said lever; and spring means engaging at one end thereof against said lever and at the other end against said bushing of said coupling means and tending to move the latter and said movable cutter connected thereto in direction of the axis of said lever toward said cutting foil whereby said spring means is stressed only due to reciprocation of said bushing in axial direction of said lever and is not stressed due to relative tilting movement of lever and plate about said transversely extending axis.

3. An arrangement as defined in claim 2 in which said trunnions are located substantially in the center of gravity of said movable cutter.

4. An arrangement as defined in claim 2 in which said plate is formed from synthetic resin and in which said resilient connecting means include two pairs of hook-shaped projections respectively arranged `on opposite sides of said opening in said plate and projecting upwardly from said plate toward said open end of said housing, and a pair of pins extending fixed to said movable cutter transverse to the axis of said lever and being resiliently engaged by said hook-shaped projections.

5. An arrangement as defined in claim 4 including an additional pair of projections each arranged in a plane of symmetry between said two pairs of hook-shaped projections and respectively engaging said pins on the sides opposite the sides engaged by said hook-shaped projections.

References Cited by the Examiner UNITED STATES PATENTS 2,304,909 12/ 1942 Hanley 30-43.9 2,331,500 10/1943 Rand 30-43.9 2,873,520 2/ 1959 Schnapp et al 30-34.1

WILLIAM FELDMAN, Primary Examiner.

M. C. KRUSE, Examiner. 

1. IN A DRY SHAVER, IN COMBINATION: A HOUSING; A CUTTING HEAD MOUNTED ON SAID HOUSING AND INCLUDING A MOVABLE CUTTER AND A STATIONARY CUTTING FOIL OVERLYING SAID MOVABLE CUTTER; OSCILLATING MEANS IN SAID HOUSING AND INCLUDING AN OSCILLATING LEVER FOR RECIPROCATING SAID MOVABLE CUTTER ALONG THE INNER SURFACE OF SAID CUTTING FOIL; COUPLING MEANS INCLUDING A BUSHING SLIDABLY MOUNTED ON SAID LEVER FOR RECIPROCATION IN AXIAL DIRECTION OF THE LATTER; A PLATE FORMED WITH A CENTRAL OPENING THERETHROUGH THROUGH WHICH SAID BUSHING EXTENDS AND BEING PIVOTALLY CONNECTED TO SAID BUSHING TILTABLE ABOUT A FIXED AXIS TRANSVERSE TO THE AXIS OF SAID LEVER; AND CONNECTING MEANS FOR RELEASABLY CONNECTING SAID MOVABLE CUTTER TO SAID PLATE; AND SPRING MEANS ENGAGING AT ONE END THEREOF AGAINST SAID LEVER AND AT THE OTHER END AGAINST SAID BUSHING OF SAID COUPLING MEANS AND TENDING TO MOVE THE LATTER AND SAID MOVABLE CUTTER CONNECTED THERETO IN DIRECTION OF THE AXIS OF SAID LEVER TOWARD SAID CUTTING FOIL WHEREBY SAID SPRING MEANS IS STRESSED ONLY DUE TO RECIPROCATION OF SAID BUSHING IN AXIAL DIRECTION OF SAID LEVER AND IS NOT STRESSED DUE TO RELATIVE TILTING MOVEMENT OF LEVER AND PLATE ABOUT SAID TRANSVERSELY EXTENDING AXIS. 